As for ordinary washing machines installed in households or laundromats, vibrations and noises are generated when laundry is biased in a dehydration tub during dehydration. The vibrations and noises may develop into trouble depending on the installation location of the washing machine and the surrounding environment. In addition, when the biasing of the laundry is relatively large, the eccentricity of the washing tub at the time of rotation becomes large, and a large torque is required for rotation, so that the dehydration operation cannot be started.
In view of this, a first conventional technique includes detecting an unbalance amount and an unbalanced position of clothes in a washing tub during dehydration and braking the rotation of the washing tub to lower the centrifugal force when there is unbalance, so that the lumps of the clothes that cause the unbalance fall by gravity and are dispersed.
In addition, a second conventional technique includes determining whether there is unbalance in a washing tub during a low-speed rotation, stopping the motor when the unbalance is detected and injecting water into the washing tub to release the lumps of clothes for eliminating the unbalance.
However, in the first conventional technique, an unbalance detection and a dispersion operation can be performed only when the dehydration tub rotates at a low speed in the dehydration processing, and the unbalance may occur again due to the influence of the type of clothes and the like after the start of the high-speed rotation of the dehydration tub.
Further, in the first and second conventional techniques, when the unbalance is detected, the rotation of the dehydration tub is decelerated or stopped, so that every time the dehydration operation is repeated, a starting power is required. Not only the power consumption is large, but also the time required for washing, i.e. the operation time, is delayed. Furthermore, in the second conventional technique, the power consumption is increased, besides, a problem exits that water consumption is also increased.
In the washing machine installed in the laundromat, in particular, the above-described delay in the driving time leads to a decrease in the circulation efficiency of the customer in the store.